1. Technical Field
The present invention relates to an image forming apparatus such as a color printer.
2. Related Art
An image forming apparatus including photosensitive drums corresponding to yellow, magenta, cyan and black, and developing units corresponding to the photosensitive drums.
In a color image formation process, each developing unit is driven and a toner image is formed on each photosensitive drum. In a monochrome image formation process, a toner image is formed only on a black photosensitive drum.
In such an image forming apparatus, a gear train for transmitting driving force to the black developing unit and a gear train for transmitting driving force to the yellow, magenta, cyan and black developing units are separately provided, and a rocking gear is provided between two gear trains. Driving force of the motor, which is rotatable in a forward direction and a reverse direction, is input in the rocking gear.
In this configuration, the motor is driven to rotate in one direction when forming a color image and in opposite direction when forming a monochrome image. Thus, it is difficult to use a motor as a driving source of other members of the color printer.